import Vue from 'vue'
  
// v-dialogDrag: 弹窗拖拽属性
Vue.directive('dialogDrag', {
  bind(el, binding, vnode, oldVnode) {
    const dialogHeaderEl = el.querySelector('.el-dialog__header')
    const dragDom = el.querySelector('.el-dialog')
    // dialogHeaderEl.style.cursor = 'move';
    dialogHeaderEl.style.cssText += ';cursor:move;'
    dragDom.style.cssText += ';top:0px;'
  
    // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
    const sty = (function() {
        if (window.document.currentStyle) {
            return (dom, attr) => dom.currentStyle[attr]
        } else
            {
            return (dom, attr) => getComputedStyle(dom, false)[attr]
        }
    })()    
     
    dialogHeaderEl.onmousedown = (e) => {
      // 鼠标按下，计算当前元素距离可视区的距离
      const disX = e.clientX - dialogHeaderEl.offsetLeft
      const disY = e.clientY - dialogHeaderEl.offsetTop
       
      const screenWidth = document.body.clientWidth // body当前宽度
        const screenHeight = document.documentElement.clientHeight // 可见区域高度(应为body高度，可某些环境下无法获取) 
         
        const dragDomWidth = dragDom.offsetWidth // 对话框宽度
        const dragDomheight = dragDom.offsetHeight // 对话框高度
         
        const minDragDomLeft = dragDom.offsetLeft
        const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth
         
        const minDragDomTop = dragDom.offsetTop
        const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight
  
      // 获取到的值带px 正则匹配替换
      let styL = sty(dragDom, 'left')
      let styT = sty(dragDom, 'top')
  
      // 注意在ie中 第一次获取到的值为组件自带50% 移动之后赋值为px
      if (styL.includes('%')) {
        styL = +document.body.clientWidth * (+styL.replace(/\%/g, '') / 100)
        styT = +document.body.clientHeight * (+styT.replace(/\%/g, '') / 100)
      } else {
        styL = +styL.replace(/\px/g, '')
        styT = +styT.replace(/\px/g, '')
      };
       
      document.onmousemove = function (e) {
        // 通过事件委托，计算移动的距离 
                let left = e.clientX - disX
                let top = e.clientY - disY
                 
                // 边界处理
                if (-(left) > minDragDomLeft) {
                    left = -(minDragDomLeft)
                } else if (left > maxDragDomLeft) {
                    left = maxDragDomLeft
                }
                 
                if (-(top) > minDragDomTop) {
                    top = -(minDragDomTop)
                } else if (top > maxDragDomTop) {
                    top = maxDragDomTop
                }
  
        // 移动当前元素 
                dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;
      }
  
      document.onmouseup = function (e) {
        document.onmousemove = null
        document.onmouseup = null
      }
    } 
  }
})